What mistakes delay ADU permits?

Most ADU permit delays trace back to a handful of avoidable mistakes — chiefly an incomplete submittal package, MEP plans missing required calculations, and a Title 24 energy report that is unregistered, on the wrong code cycle, or inconsistent with the plans. The good news is that nearly all of them are preventable with coordinated, permit-ready documents.

The most common MEP plan mistakes

1. Missing load calculations. An electrical plan without a formal NEC Article 220 load calculation, or a mechanical plan without a Manual J heat load calculation, is one of the most frequent correction triggers.
2. Incomplete panel schedules. The schedule must list every circuit with description, amperage, and voltage. Gaps draw corrections.
3. GFCI/AFCI notation absent. Reviewers expect the plans to clearly call out which outlets are GFCI-protected and which circuits are AFCI-protected.
4. EV-ready conduit not shown. California requires EV-ready infrastructure on new ADUs, and it is routinely overlooked.
5. Missing DWV vent design. A plumbing plan that omits the vent stacks, slope, or cleanouts is a classic correction.
6. Equipment not specified. HVAC, water heater, and fixtures must be listed with make and model so the reviewer can check them against Title 24 and CALGreen minimums.

Title 24 and energy-code mistakes

• Unregistered CF1R — submitting a plain PDF that hasn't been registered with an Energy Code Compliance Provider. Building departments require the registered version.
• Wrong code cycle — using outdated software for a permit submitted on or after the current code's effective date (the 2025 energy code applies to applications submitted on or after January 1, 2026).
• Wrong climate zone — California has 16 climate zones, determined by parcel address, not city or ZIP. A wrong zone produces invalid results.
• Wrong compliance path for the ADU type — applying new-construction rules to a garage conversion, which is an alteration.
• CF1R and MEP plans inconsistent — equipment on the plans not matching the efficiency specs in the energy report.

Process and coordination mistakes

Beyond the documents themselves, projects stall when the architectural, structural, and MEP drawings conflict — for example, outlet or fixture locations that don't match the actual wall and kitchen layout. Submitting an incomplete package (missing a site plan, a required form, or owner authorization) triggers an incomplete notice that resets the clock before plan check even begins.

The single best defense is coordination: when MEP plans and the Title 24 report are prepared by the same team and reconciled with the architectural set before submittal, the most common correction sources simply disappear.

Every order from us includes two revisions and city corrections at no extra charge, so if a comment does come back, we handle it. To minimize corrections from the start, consider bundling your Title 24 report with your MEP plans, and review the permit guide before you submit. Requirements vary by jurisdiction — confirm specifics with your local building department.